Low Temperature Fuel Cell Catalyst Preparation And Its Application

Proton exchange membrane fuel cell(PEMFC) has received significant attention for its special property of high energy density, low operation temperature, no corrosion problem, and so on. The electrocatalytic activity of catalysts is still thought as the most challenging problem for the development of PEMFC and the nature and structure of catalysts were significantly influenced by the preparation procedure of catalysts. Considering this problem, the emphasis of this paper was placed on exploiting electrocatalysts with better properties and providing reference for preparing catalysts.Carbon supported Pt-based catalysts for PEMFC were prepared by using XC-72 carbon as supporter. Three methods, impregnation-reduction of metal precursors by formaldehyde, the oxidative decomposition of sodium sulphites of platinum or/and ruthenium by H₂O₂ and the improved impregnation-reduction method, were utilized. The results of XRD and TEM demonstrated that there were crystalline face-centered cubic phases in the Pt/C, PtRu/C catalysts and PtRu alloy in PtRu/C catalysts, but there were no metal Ru and its oxide. Nanoparticles in Pt/C catalysts prepared by improved impregnation-reduction method were small and uniform.The electrochemical properties of Pt/C and PtRu/C catalysts were studied by several technologies such as Cyclic Voltammetry and A.C. Impedance technique. The results revealed that the activity of these catalysts decreased in the order: the improved impregnation-reduction method＞the impregnation-reduction of metal precursors by formaldehyde＞the oxidative decomposition of sodium sulphites of platinum or/and ruthenium by H₂O₂. In addition, the catalysts prepared by improved impregnation-reduction method had the highest oxidation current and the lowest impedance.The result showed that this way was an efficient way to increase methanol-tolerant ability of Pt/C catalysts.A DMFC and a PEMFC single cell with home-made catalysts and membrane electrode assembly operating at ambient oxygen pressure and room temperature were fabricated and tested. The DMFC's maximum power density was 2.42mW/cm² and it yielded a current density of 10mA/cm² at 0.22V cell voltage. The PEMFC's maximum power density was 36mW/cm² and it yielded a current density of 50mA/cm² at 0.49V cell voltage.